Mica

Physical Properties

Hardness: 2.5–3.0 on Mohs scale; Color: Golden-brown to bronze; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets); Specific gravity: 2.7–3.3

Formation & Geological History

Formed in igneous environments like pegmatites and metamorphic rocks such as marbles and schists. Phlogopite typically forms through the metamorphism of magnesium-rich limestones and dolomites.

Uses & Applications

Used as an electrical insulator, in spark plugs, as an ingredient in joint compound, and in cosmetics to provide shimmer.

Geological Facts

Mica sheets were historically used as windows for stoves because they are transparent and can withstand very high temperatures without melting or cracking.

Field Identification & Locations

Identify by its 'book-like' appearance and ability to peel off paper-thin, flexible flakes with a fingernail. Commonly found in coarse-grained igneous and metamorphic terrains.

Identified on: 5/7/2026

Mode: Standard